Method of forming multilayer titanium nitride film by multiple step chemical vapor deposition process and method of manufacturing semiconductor device using the same

ABSTRACT

A method of forming a multilayer titanium nitride film hardly containing any Cl component by a multiple step chemical vapor deposition method, and a method of manufacturing a semiconductor device using the same are provided. In the present invention, a multilayer TiN film is formed by multiple step chemical vapor deposition (CVD) on a semiconductor substrate on which an underlayer is formed. In order to form the multilayer TiN film, an underlayer protective TiN film is formed by forming a first TiN film on the underlayer and NH 3  annealing the first TiN film. A main TiN film is formed by forming a second TiN film on the underlayer protective TiN film and NH 3  annealing the second TiN film. A source gas used in order to form the first TiN film has a smaller TiCl 4  to NH 3  gas flow ratio than a source gas for forming the second TiN film. In order to apply the multilayer TiN film to the fabrication of the semiconductor device, an insulating film having a contact hole is formed on a semiconductor substrate. A Ti film is formed on the inner wall of the contact hole. A multilayer TiN film is formed on the Ti film by the multiple step CVD method. A metal plug is formed on the multilayer TiN film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing asemiconductor device, and more particularly, to a method of forming atitanium nitride film and a method of manufacturing a semiconductordevice using the same.

2. Description of the Related Art

An adhesive layer having a Ti/TiN structure is generally employed inorder to improve the poor adhesive characteristic of a metal such astungsten (W) for filling a contact hole, when a metal contact plugrequired for the metal wiring of a semiconductor device is formed.

In a conventional technology, a physical vapor deposition (PVD) methodsuch as a sputtering method is used for forming the adhesive layerhaving the Ti/TiN structure. However, when the Ti/TiN structure isformed by the PVD method, a film having a poor step coverage isobtained. Therefore, in the case of forming a contact having a largeaspect ratio, the overhang of the Ti/TiN film is severe at the entranceof the contact hole when the Ti/TiN film is used as the adhesive layeror a barrier layer. Accordingly, a large void is formed in the contactduring a subsequent process of depositing a tungsten film. Also, whenthe Ti/TiN film is too thin on the bottom of the contact due to the poorstep coverage of the Ti/TiN film, WF₆ gas, used as a source gas during asubsequent process of depositing the tungsten film, and Ti of the Ti/TiNfilm react, thus forming a nonconductor or vaporizing some part.Accordingly, the TiN film is lifted and peeled off. If so, the Ti/TiNfilm cannot serve as a barrier with respect to the WF₆ gas.

Therefore, a process of forming a TiN film by a chemical vapordeposition (CVD) method has been recently developed.

In particular, the TiN film formed by the CVD method using TiCl₄ gas asa source gas is generally used as an adhesive layer of a metal film or abarrier film when a metal contact or a capacitor is formed since it ispossible to obtain a good step coverage.

A large amount of chlorine (Cl) is included in the formed TiN film inthe method of forming the TiN film by the CVD method using the TiCl₄ gasas the source gas. The TiN film containing a large amount of Cl shows ahigh resistivity. Also, since Cl permeates and damages the Ti film whichis an underlayer, a high temperature rapid thermal nitration (RTN)process, or an NH₃ plasma process is required on the Ti film in order toprevent the Cl permeation.

When the high temperature RTN process or the NH₃ plasma process isperformed with respect to the Ti film, the following problems occur.Firstly, the number of processes increases and a semiconductormanufacturing process becomes complicated since the above process isadded. Secondly, additional equipment should be introduced since theabove process is added. As a result, the burden of equipment investmentincreases. Thirdly, shallow junctions have recently started to berealized in semiconductor devices. Therefore, the allowed thickness ofthe Ti film deposited as the barrier film in the contact hole isrestricted. However, a considerable amount of Ti is consumed in the Tifilm by the high temperature RTN process or the NH₃ plasma process. As aresult, it is not possible to secure a stable contact resistance sincethe amount of residing Ti becomes small.

SUMMARY OF THE INVENTION

To solve the above problem(s), it is an objective of the presentinvention to provide a method of forming a multilayer TiN film so as tolower the amount of Cl in a TiN film introduced when the TiN film isformed by a chemical vapor deposition (CVD) method such that the devicedoes not deteriorate.

It is another objective of the present invention to provide a method ofmanufacturing a multilayer TiN film by which it is possible to simplifya process by reducing the number of process steps.

It is still another objective of the present invention to provide amethod for manufacturing a semiconductor device using the TiN filmformed by the above method.

Accordingly, to achieve the first and second objectives, there isprovided a method of forming a multilayer TiN film by a chemical vapordeposition (CVD) method on a semiconductor substrate on which anunderlayer is formed. In this method, an underlayer protective TiN filmis formed on the underlayer. A main TiN film is formed on the underlayerprotective TiN film.

The underlayer is a Ti film. At this time, NH₃ gas may be pre-flown onthe surface of the Ti film before the step (a).

The step (a) comprises the steps of (a-1) forming a first TiN film onthe underlayer to have a thickness of between 10 and 100 Å using asource gas composed of a mixture of TiCl₄ gas and NH₃ gas and (a-2)annealing the first TiN film in an NH₃ gas atmosphere.

The step (b) comprises the steps of (b-1) forming a second TiN film onthe underlayer protective TiN film using a source gas formed of amixture of TiCl₄ gas and NH₃ gas and (b-2) annealing the second TiN filmin the NH₃ gas atmosphere.

The gas flow ratio of TiCl₄ to NH₃ is between 0.02 and 0.1 in the sourcegas.

The first and second TiN films are formed under a pressure of between0.2 and 0.5 Torr and at a temperature of between 530 and 680° C.

The steps of annealing the first TiN film and the second TiN film arerespectively performed at a temperature of between 530 and 680° C.

The step (c) of forming an oxygen diffusion preventing TiN film on themain TiN film can be further comprised after the step (b).

The step (c) comprises the steps of (c-1) forming a third TiN film onthe main TiN film using a source gas composed of a mixture of TiCl₄ gasand NH₃ gas, to have a thickness of between 10 and 100 Å and (c-2)annealing the third TiN film in the NH₃ gas atmosphere.

The third TiN film is formed under a pressure of between 0.2 and 0.5Torr and at a temperature of between 530 and 680° C.

In order to form the main TiN film, a TiN film is formed on theunderlayer protective TiN film to have a thickness of between 10 and 100Å using a source gas formed of a mixture of TiCl₄ gas and NH₃ gas. TheTiN film is annealed in an NH₃ gas atmosphere. The above steps arerepeated until the main TiN film having a desired thickness is obtained.

Also, to achieve the above objectives, a first TiN film covering theunderlayer exposed on a semiconductor substrate is formed by a chemicalvapor deposition (CVD) method using a source gas supplied in a first gasflow ratio having a predetermined TiCl₄ to NH₃ gas flow ratio. The firstTiN film is annealed in an NH₃ gas atmosphere to form an underlayerprotective TiN film. A second TiN film is formed on the underlayerprotective TiN film by the CVD method, using a source gas supplied in asecond gas flow ratio having a TiCl₄ to NH₃ gas flow ratio larger thanthe first gas flow ratio. The second TiN film is annealed in an NH₃ gasatmosphere to form a main TiN film.

The first gas flow ratio and the second gas flow ratio are selected tobe between 0.02 and 0.1, respectively. The first gas flow ratio isselected to be between 0.02 and 0.05.

The step of forming the first TiN film and the step of forming thesecond TiN film are respectively performed under a pressure of between0.2 and 0.5 Torr and at a temperature of between 530 and 680° C.

The steps of annealing the first TiN film and the second TiN film arerespectively performed at a temperature of between 530 and 680° C.

After forming the main TiN film, a third TiN film is formed on the mainTiN film using a source gas supplied in a third gas flow ratio having aTiCl₄ to NH₃ gas flow ratio which is smaller than the second gas flowratio. The third TiN film is annealed in an NH₃ gas atmosphere.

The third gas flow ratio is selected to be between 0.02 and 0.1.

Also, to achieve the above objectives, in the present invention, a firstTiN film covering the underlayer exposed on a semiconductor substrate bythe CVD method, using a source gas supplied in a first gas flow ratiohaving a predetermined TiCl₄ to NH₃ gas flow ratio. A second TiN film isformed on the first TiN film by the CVD method, using a source gassupplied in a second gas flow ratio having a TiCl₄ to NH₃ gas flow ratiowhich is larger than the first gas flow ratio. The first TiN film andthe second TiN film are annealed in a NH₃ gas atmosphere.

To achieve the third objective, in a method of manufacturing asemiconductor substrate according to the present invention, aninsulating film having a contact hole is formed on a semiconductorsubstrate. A Ti film is formed on the inner wall of the contact hole. Amultilayer TiN film is formed by repeating a process of forming a TiNfilm on the Ti film by a CVD method using a source gas composed of amixture of TiCl₄ gas and NH₃ gas and annealing the TiN film in an NH₃gas atmosphere at least two times. A metal plug is formed on themultilayer TiN film.

According to the present invention, it is possible to obtain a densifiedmultilayer TiN film sufficiently removed of the Cl component so that thedevice is not deteriorated. When the multilayer TiN film according tothe present invention is used as a barrier film of a metal contact, itis possible to reduce the resistance of the contact and to omit anadditional process such as a high temperature rapid thermal nitration(RTN) process for protecting an underlayer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objectives and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIGS. 1A through 1F are cross sectional views for describing a method offorming a multilayer TiN film according to a first embodiment of thepresent invention;

FIGS. 2A and 2B are cross sectional views for describing a method offorming a multilayer TiN film according to a second embodiment of thepresent invention;

FIGS. 3A through 3F are cross sectional views for describing a method offorming a multilayer TiN film according to a third embodiment of thepresent invention;

FIGS. 4A through 4C are cross sectional views for describing a method offorming a multilayer TiN film according to a fourth embodiment of thepresent invention;

FIG. 5 is a graph showing the resistivities of a multilayer TiN filmformed according to the present invention and TiN films formed by aconventional method; and

FIGS. 6A through 6E are cross sectional views for describing a method ofmanufacturing a semiconductor device according to a preferred embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the attached drawings.

FIGS. 1A through 1F are cross sectional views showing processes of amethod of forming a multilayer TiN film by a multiple step chemicalvapor deposition (CVD) process according to a first embodiment of thepresent invention.

Referring to FIG. 1A, an underlayer 10 such as a Ti film is formed on asemiconductor substrate (not shown). The underlayer 10 may be TaO or Pt.A first TiN film 22 is formed on the underlayer 10 by a chemical vapordeposition (CVD) method using a mixture of TiCl₄ gas and NH₃ gas as asource gas, to have a thickness of between 10 and 100 Å in the firststep of forming a multilayer TiN film by a multiple step deposition. Thedeposition process is performed at a temperature of between 530 and 680°C. Here, the first TiN film 22 is formed on the underlayer 10 throughthermal reduction of the TiCl₄ gas with the NH₃ gas in the source gas.

At this time, the flow rates of the TiCl₄ gas and the NH₃ gas, each ofwhich compose the source gas, are controlled so as to obtain a TiCl₄ toNH₃ gas flow ratio of between 0.02 and 0.1. The reaction pressure duringthe formation of the first TiN film 22 is between 0.2 and 0.5 Torr.

Preferably, an NH₃ pre-flow step of providing the NH₃ gas on the surfaceof the underlayer 10 may be performed before forming the first TiN film22. The NH₃ pre-flow step is performed for 60 seconds at a temperatureof between 530 and 680° C. and under a pressure of 0.3 Torr.

Referring to FIG. 1B, the first TiN film 22 is annealed in an NH₃ gasatmosphere. For this, the NH₃ gas is provided on the first TiN film 22at the temperature of between 530 and 680° C. As a result, a Clcomponent existing on the surface or the grain boundary of the first TiNfilm 22 is completely removed and the place from which Cl is removed isfilled with an N component. Accordingly, the first TiN film 22 isdensified. Therefore, an underlayer protective TiN film 22 a whichcontains few Cl component is formed. Also, there are few Cl componentsin the interface between the underlayer protective TiN film 22 a and theunderlayer 10. For example, the NH₃ gas of 1,000 sccm is supplied for 60seconds under a pressure of 3 Torr and at the temperature of between 530and 680° C., for the NH₃ annealing.

The underlayer protective TiN film 22 a obtained after the NH₃ annealingis sufficiently removed of the Cl component and the place from which Clis removed is filled with the N component. Accordingly, the underlayerprotective TiN film 22 a is densified. Therefore, it is difficult forthe Cl component to permeate the underlayer protective TiN film 22 afrom the TiCl₄ gas when a TiN film is formed using the TiCl₄ gas in asubsequent process. Therefore, it is possible to prevent the underlayer10 from being damaged by the Cl component.

Referring to FIG. 1C, a second TiN film 24 is formed on the underlayerprotective TiN film 22 a to a predetermined thickness. The thickness ofthe second TiN film 24 is determined considering the thicknesses of theunderlayer protective TiN film 22 a according to the total thickness ofthe multilayer TiN film to be formed. The deposition conditions at thistime are the same as those of forming the first TiN film 22 describedwith reference to FIG. 1A.

Referring to FIG. 1D, a main TiN film 24 a removed of the Cl componentcontained in the second TiN film 24 and having a densified structure isformed by annealing the second TiN film 24 in the NH₃ gas atmosphere bythe same method as that described with reference to FIG. 1B.

It is possible to prevent the Cl component from permeating into theunderlayers of the main TiN film 24 a during the subsequent process ofdepositing a TiN film on the main TiN film 24 a using the TiCl₄ gassince the main TiN film 24 a removed of the Cl component has a densifiedstructure.

Referring to FIG. 1E, a third TiN film 26 is formed on the main TiN film24 a by the same method as that of forming the first TiN film 22described with reference to FIG. 1A, to have the thickness of between 10and 100 Å.

Referring to FIG. 1F, the Cl component is removed from the third TiNfilm 26 by annealing the third TiN film 26 in a NH₃ gas atmosphere, anda densified oxygen diffusion preventing TiN film 26 a is formed by thesame method as that described with reference to FIG. 1B.

The multilayer TiN film 20 formed of the underlayer protective TiN film22 a, the main TiN film 24 a, and the oxygen diffusion preventing TiNfilm 26 a is formed on the underlayer 10 by a multiple step CVD method.

As mentioned above, when the semiconductor substrate on which themultilayer TiN film 20 is formed is exposed to the air for a subsequentprocess after forming the multilayer TiN film 20 by the CVD method, itis possible to prevent oxygen in the air from permeating the multilayerTiN film 20 by the oxygen diffusion preventing TiN film 26 a formed onthe surface of the multilayer TiN film 20. Therefore, it is possible toprevent the resistivity from increasing due to the permeation of oxygeninto the multilayer TiN film 20 including the oxygen diffusionpreventing TiN film 26 a formed by the multiple step CVD method.

In the above embodiment, the multilayer TiN film is formed by a threestep deposition process. However, the present invention is notrestricted to this.

For example, if the increase of the resistivity according to thepermeation of oxygen is negligible, thus not deteriorating the device,the process of forming the oxygen diffusion preventing TiN film 26 a canbe omitted in order to simplify processes and to save expenses.

Also, it is possible to form a multilayer TiN film comprised of three ormore layers by a multiple step CVD method as follows, instead of formingthe multilayer TiN film by the three step deposition process asmentioned in the above embodiment.

FIGS. 2A and 2B are cross sectional views showing processes of themethod of forming the multilayer TiN film by the multiple step CVDprocess according to a second embodiment of the present invention.

Referring to FIG. 2A, after forming an underlayer 50 on a semiconductorsubstrate (not shown) by the same method as that described withreference to FIG. 1A, an underlayer protective TiN film 62 a is formedon the underlayer 50 to have a thickness of between 10 and 100 Å. Asecond TiN film 64 is formed on the underlayer protective TiN film 62 aby the same method as the method of forming the first TiN film 22described with reference to FIG. 1A, to have a thickness of between 10and 100 Å.

Referring to FIG. 2B, the Cl component contained in the second TiN film64 is completely removed by annealing the second TiN film 64 in an NH₃gas atmosphere by the same method as that describe with reference toFIG. 1B. Accordingly, a densified first main TiN film 64 a is formed.

Then, a plurality of main TiN films are formed to have a desiredthickness by sequentially forming a second main TiN film (not shown), athird main TiN film (not shown), . . . on the first main TiN film 64 aby repeating the step of forming the TiN film of FIG. 2A and the NH₃annealing step of FIG. 2B as many times as required with respect to theresultant material in which the first main TiN film 64 a is formed.

The method according to the second embodiment, described with referenceto FIGS. 2A and 2B, may require a longer process time than the methodaccording to the first embodiment, described in FIGS. 1A through 1F.However, the TiN film obtained by the method according to the secondembodiment contains less Cl component and is more dense.

FIGS. 3A through 3F are cross sectional views showing processes of themethod of forming a multilayer TiN film by the multiple step CVD processaccording to a third embodiment of the present invention.

Referring to FIG. 3A, an underlayer 70 such as a Ti film is formed onthe semiconductor substrate (not shown). A first TiN film 72 is formedon the underlayer 70, to a thickness of between 10 and 100 Å, by the CVDmethod under a pressure of between 0.2 and 0.5 Torr and at a temperatureof between 530 and 680° C., using a source gas composed of a mixture ofthe TiCl₄ gas and the NH₃ gas supplied in a first gas flow ratio ofTiCl₄ to NH₃ selected from a value between 0.02 and 0.1 and having arelatively low Cl content. Preferably, the first gas flow ratio isselected from a value between 0.02 and 0.05, more preferably, from avalue between 0.03 and 0.04.

Referring to FIG. 3B, the first TiN film 72 is annealed in an NH₃atmosphere at a temperature of between 530 and 680° C. As a result, theCl component existing on the surface of the first TiN film 72 or thegrain boundary in the first TiN film 72 is completely removed and theplace from which Cl is removed is filled with an N component.Accordingly, the first TiN film 72 is densified. Therefore, anunderlayer protective TiN film 72 a which contains a small amount of theCl component is formed on the underlayer 70. Also, there is a smallamount of the Cl component in the interface between the underlayerprotective TiN film 72 a and the underlayer 70. For example, the NH₃ gasof 1,000 sccm is supplied for 60 seconds under the pressure of 3 Torrand at the temperature of between 530 and 680° C., for the NH₃annealing.

Since the underlayer protective TiN film 72 a is obtained by depositingthe first TiN film 72 using a source gas containing a relatively lowcontent of Cl and by sufficiently removing the Cl component residing inthe TiN film 72, it is possible to contact the underlayer protective TiNfilm 72 a, completely removed of the Cl component, to the underlayer 70.Also, in the underlayer protective TiN film 72 a, the place from whichCl is removed is filled with an N component by the NH₃ annealing.Accordingly the underlayer protective TiN film 72 a is densified.Therefore, it is difficult for the Cl component to permeate theunderlayer protective TiN film 72 a from the TiCl₄ gas when a TiN filmis formed, using the TiCl₄ gas in a subsequent process, on theunderlayer protective TiN film 72 a. Therefore, it is possible toprevent the underlayer 70 from being damaged by the Cl component.

Referring to FIG. 3C, a second TiN film 74 is formed on the underlayerprotective TiN film 72 a to have a predetermined thickness, by the CVDmethod, using a source gas supplied in a second gas flow ratio of TiCl₄to NH₃ selected from a value between 0.02 and 0.1 and larger than thefirst gas flow ratio, so as to have a larger content of Cl than in thesource gas supplied in the first gas flow ratio. The thickness of thesecond TiN film 74 is determined considering the thicknesses of theunderlayer protective TiN film 72 a according to the total thickness ofthe multilayer TiN film to be formed. The deposition temperature and thepressure condition at this time are the same as those of forming thefirst TiN film 72 described with reference to FIG. 3A.

Referring to FIG. 3D, the second TiN film 74 is annealed in the NH₃atmosphere and the Cl component contained in the second TiN film 74 isremoved by the same method as that described with reference to FIG. 3B.Accordingly, a densified main TiN film 74 a is formed.

Referring to FIG. 3E, a third TiN film 76 is formed on the main TiN film74 a to have a thickness of between 10 and 100 Å by the same method asthe method of forming the first TiN film 72 described with reference toFIG. 3A. A source gas supplied in a third flow ratio of TiCl₄ to NH₃selected from a value between 0.02 and 0.1 and smaller than the secondgas flow ratio so as to contain a smaller content of Cl than in thesource gas supplied in the second gas flow ratio.

Referring to FIG. 3F, a densified oxygen diffusion preventing TiN film76 a is formed by annealing the third TiN film 76 in the NH₃ gasatmosphere and removing the Cl component from the third TiN film 76 bythe same method as that described with reference to FIG. 3B.

A multilayer TiN film 78 comprised of the underlayer protective TiN film72 a, the main TiN film 74 a, and the oxygen diffusion preventing TiNfilm 76 a is formed on the underlayer 70 by the multiple step CVDmethod.

The step of forming the oxygen diffusion preventing TiN film 76 adescribed with reference to FIGS. 3E and 3F can be omitted if necessary.

It is possible to prevent oxygen in the air from permeating themultilayer TiN film 78, since the multilayer TiN film 78 has a densifiedstructure, when the semiconductor substrate on which the multilayer TiNfilm 78 is formed is exposed to air in order to perform a subsequentprocess. Therefore, it is possible to prevent the resistivity fromincreasing due to the permeation of oxygen in the multilayer TiN film 78formed by the multiple step CVD method.

FIGS. 4A through 4C are cross sectional views showing processes of themethod of forming a multilayer TiN film by the multiple step CVD methodaccording to a fourth embodiment of the present invention.

Referring to FIG. 4A, an underlayer 80, for example, a Ti film is formedon a semiconductor substrate (not shown). A first TiN film 82 is formedon the underlayer 80 to have a thickness of between 10 and 100 Å by theCVD method under a pressure of between 0.2 and 0.5 Torr and at atemperature of between 530 and 680° C., using a source gas composed of amixture of the TiCl₄ gas and the NH₃ gas supplied in a first gas flowratio of TiCl₄ to NH₃ selected from a value between 0.02 and 0.1 andhaving a relatively low Cl component. Preferably, the first gas flowratio is selected between 0.02 and 0.05, more preferably, from a valuebetween 0.03 and 0.04.

Referring to 4B, a second TiN film 84 is formed on the first TiN film 82by the CVD method, to have a predetermined thickness, using a source gassupplied in a second gas flow ratio of TiCl₄ to NH₃ selected between0.02 and 0.1 and larger than the first gas flow ratio so as to have alarger content of Cl than in the source gas supplied in the first gasflow ratio. The thickness of the second TiN film 84 is determinedconsidering the thicknesses of the first TiN film 82 according to thetotal thickness of the multilayer TiN film to be formed. The depositiontemperature and the pressure condition at this time are the same asthose of forming the first TiN film 82 described with reference to FIG.4A.

Referring to 4C, the resultant obtained by sequentially stacking thefirst TiN film 82 and the second TiN film 84 is annealed in a NH₃ gasatmosphere at a temperature of 530 to 680° C. For the NH₃ annealing,1,000 sccm of the NH₃ gas is supplied for 60 seconds under a pressure of3 Torr and at the temperature of between 530 and 680° C. As a result,the Cl component existing on the surfaces or the grain boundaries of thefirst and second TiN films 82 and 84 is completely removed and the placefrom which Cl is removed is filled with the N component, thus obtaininga multilayer TiN film 88 comprised of the densified underlayerprotective TiN film 82 a and main TiN film 84 a.

In the present embodiment, the step of NH₃ annealing the first TiN film82 was omitted before forming the second TiN film 84. However, thestructure of the multilayer TiN film 88 in which the surface and insidethereof is completely removed of the Cl component by the above method isdensified. Therefore, although the multilayer TiN film 88 is exposed toair, it is possible to prevent oxygen from permeating the multilayer TiNfilm 88. Therefore, it is possible to prevent the resistivity fromincreasing due to the permeation of oxygen into the multilayer TiN film88.

FIG. 5 is a graph showing the result of comparing the resistivity of themultilayer TiN film formed by the multiple step CVD method according tothe present invention with the resistivity of the TiN film formed by theconventional method.

In FIG. 5, (a) shows a case of a multilayer TiN film formed by amultilayer deposition method according to the present invention. To bespecific, a multilayer TiN film having a thickness of 500 Å is formed bysuccessively repeating the process of NH₃ annealing the TiN filmobtained after forming the TiN film having a thickness of 50 Å by theCVD method 10 times. The characteristics denoted by (b) and (c) showcases in which the TiN film having the thickness of 500 Å is depositedin one step by the CVD method and the NH₃ gas is supplied to the TiNfilm. To be specific, (b) shows a case in which 1,000 sccm of NH₃ gas issupplied at a temperature of 680° C. and under a relatively highpressure of 3 Torr. (c) shows a case in which 400 sccm of the NH₃ gas issupplied at a temperature of 680° C. and under a relatively low pressureof 0.3 Torr. The characteristic denoted by (d) shows a case in which aTiN film having a thickness of 500 Å is deposited in one step by the CVDmethod, in which the step of providing the NH₃ gas is omitted.

It is noted from the result of FIG. 5 that the multilayer TiN filmformed by the multiple step deposition method according to the presentinvention has much lower resistivity than the conventional methods.

As a result, it is noted that the multilayer TiN film formed by themultiple step CVD method according to the present invention contains anextremely small content of Cl and hardly undergoes increment of theresistivity due to substitution of oxygen when the multilayer TiN filmis exposed to air.

Also, the Ti film is not damaged at all by the Cl component during theformation of the TiN film and the lifting of the TiN film is preventedby forming the multilayer TiN film on the Ti film by the multiple stepCVD method according to the present invention without performing the RTNprocess or the NH₃ plasma process after forming the Ti film. As aresult, it is possible to form a TiN film having low resistivity byforming the TiN film to have a small amount of Cl by the multiple stepCVD method.

Therefore, it is possible to reduce contact resistance when themultilayer TiN film formed by the above method is employed as a barrierfilm in a metal contact.

FIGS. 6A through 6E are cross sectional views showing processes of amethod of manufacturing a semiconductor device according to a preferredembodiment of the present invention.

Referring to FIG. 6A, an interlayer dielectric film 110 having a contacthole H for exposing a part of a conductive layer (not shown), which isformed on a semiconductor substrate 100.

Referring to FIG. 6B, a Ti film 120 is formed on the resultant in whichthe contact hole H is formed by a sputtering method or the CVD method tohave a thickness of about between 300 and 900 Å.

Referring to FIG. 6C, a multilayer TiN film 130 is formed on the Ti film120 using a source gas comprised of TiCl₄ gas and NH₃ gas.

The multilayer TiN film 130 is obtained by forming a Ti film protectiveTiN film 132, a main TiN film 134, and an oxygen diffusion preventingTiN film 136 by the same method as that of the first embodiment. Themain TiN film 134 can be formed of a single film formed by the singlestep CVD process. However, it may be formed of a multilayer film formedby the multiple step CVD process.

When the main TiN film 134 is formed of a multilayer film, the main TiNfilm 134 having a desired thickness is formed by repeating, as manytimes as required, the step of forming a TiN film on the Ti protectingTiN film 132, by the CVD method to have a thickness of between 10 and100 Å and the step of NH₃ annealing the TiN film, thus removing the Clcomponent in the TiN film and densifying the TiN film.

In the present embodiment, the multilayer TiN film 130 is described tobe comprised of the Ti protecting TiN film 132, the main TiN film 134,and the oxygen diffusion preventing TiN film 136. However, the presentinvention is not restricted to this.

For example, the oxygen diffusion preventing TiN film 136 can be omittedin order to simplify the process and to save expenses when the increaseof resistivity according to the permeation of oxygen is negligible, thusnot deteriorating the device.

Referring to FIG. 6D, a metal layer 140 is formed by depositing a metalsuch as tungsten on the resultant in which the multilayer TiN film 130is formed so as to fill the inside of the contact hole H.

Referring to FIG. 6E, the upper surface of the interlayer dielectricfilm 110 is exposed by polishing the resultant in which the metal layer140 is formed by a chemical mechanical polishing method, and a barrierfilm comprised of the Ti film 120 and the multilayer TiN film 130 and ametal plug 140 a on the barrier film are formed in the contact hole H.

As mentioned above, when the multilayer TiN film formed by a multiplestep CVD method is used as a TiN film constructing the barrier film ofthe Ti/TiN structure in order to form the contact of a semiconductordevice, it is possible to prevent the Ti film from being damaged, toprevent the TiN film from being lifted by the multilayer TiN film whichdoes not contain the Cl component, and to remarkably lower resistivityin the TiN film, without performing a subsequent process such as the RTNprocess after forming the Ti film.

In the method for manufacturing a semiconductor device according to thepresent embodiment, only the case in which the method of forming themultilayer TiN film according to the first embodiment is described.However, the present invention is not restricted to this. The multilayerTiN film formed by all methods provided in the detailed description ofthe present invention, and methods which can be varied within the scopeof the present invention by anyone skilled in the art, can be applied tothe process of forming the contact of the semiconductor device.

As mentioned above, when the multilayer TiN film is formed by themultiple step CVD method according to the present invention, it ispossible to completely remove the Cl component in the TiN film and tomake the TiN film dense. Therefore, it is possible to prevent the Clcomponent of the source gas TiCl₄ from permeating into the Ti film whichis the underlayer of the TiN film, during the process of depositing theTiN film on the Ti film. Accordingly, it is possible to prevent theunderlayer from being damaged by the Cl component and to prevent the TiNfilm formed on the underlayer from being lifted.

Also, since the multilayer TiN film formed by the multiple stepdeposition method according to the present invention does not containthe Cl component and is dense, the resistivity in the TiN film isremarkably low. Therefore, when the multilayer TiN film formed by themethod according to the present invention is used as the barrier film ofa contact, it is possible to reduce the resistance of the contact and toprevent voids from being formed in the contact since the step coverageof the barrier film is excellent.

The present invention is not restricted to the above embodiments, and itis clearly understood that many variations are possible within the scopeand spirit of the present invention by anyone skilled in the art.

What is claimed is:
 1. A method of forming titanium nitride compositelayer, comprising the steps of: depositing a first titanium nitridelayer on a substrate by exposing the substrate to a first composite gasconsisting essentially of TiCl₄ and NH₃ at respective first levels thatestablish a first ratio of TiCl₄ to NH₃ in a range between about 0.02and 0.05 so that a ratio of chlorine atoms to nitrogen atoms in thefirst composite gas is in a range between about 0.08 and 0.2; annealingthe first titanium nitride layer by exposing the first titanium nitridelayer to a gas consisting essentially of NH₃; and depositing a secondtitanium nitride layer on the first titanium nitride layer by exposingthe first titanium nitride layer to a second composite gas consistingessentially of TiCl₄ and NH₃ at respective second levels that establisha second ratio of TiCl₄ to NH₃ that is greater than the first ratio. 2.The method of claim 1, further comprising the steps of: annealing thesecond titanium nitride layer by exposing the second titanium nitridelayer to a gas consisting essentially of NH₃; and depositing a thirdtitanium nitride layer on the second titanium nitride layer by exposingthe second titanium nitride layer to a third composite gas containingTiCl₄ and NH₃ at respective third levels that establish a third ratio ofTiCl₄ to NH₃ that is less than the second ratio.
 3. The method of claim2, wherein the second titanium nitride layer is thicker than the firstand third titanium nitride layers.
 4. The method of claim 2, wherein thefirst ratio equals the third ratio.
 5. The method of claim 1, whereinsaid step of depositing a first titanium nitride layer is preceded bythe step of exposing the substrate to a gas consisting essentially ofNH₃.
 6. The method of claim 1, wherein said step of depositing a firsttitanium nitride layer is preceded by the step of exposing the substrateto a gas consisting essentially of NH₃ for a duration of about 60seconds and at a temperature in a range between 530° C. and 680° C.
 7. Amethod of forming titanium nitride composite layer, comprising the stepsof: depositing a first titanium nitride layer on a substrate by exposingthe substrate to a first composite gas consisting essentially of TiCl₄and NH₃ at respective first levels that establish a first ratio of TiCl₄to NH₃ in a range between about 0.02 and 0.05 so that a ratio ofchlorine atoms to nitrogen atoms in the first composite gas is in arange between about 0.08 and 0.2; and depositing a second titaniumnitride layer on the first titanium nitride layer by exposing the firsttitanium nitride layer to a second composite gas containing TiCl₄ andNH₃ at respective second levels that establish a second ratio of TiCl₄to NH₃ that is greater than the first ratio.
 8. The method of claim 7,further comprising the steps of: annealing the second titanium nitridelayer by exposing the second titanium nitride layer to a gas consistingessentially of NH₃; and then depositing a third titanium nitride layeron the second titanium nitride layer by exposing the second titaniumnitride layer to a third composite gas containing TiCl₄ and NH₃ atrespective third levels that establish a third ratio of TiCl₄ to NH₃that is less than the second ratio.
 9. The method of claim 8, whereinthe second titanium nitride layer is thicker than the first and thirdtitanium nitride layers.
 10. The method of claim 7, wherein said step ofdepositing a first titanium nitride layer is preceded by the step ofexposing the substrate to a gas consisting essentially of NH₃.
 11. Themethod of claim 7, wherein said step of depositing a first titaniumnitride layer is preceded by the step of exposing the substrate to a gasconsisting essentially of NH₃ for a duration of about 60 seconds and ata temperature in a range between 530° C. and 680° C.
 12. The method ofclaim 7, wherein said step of depositing a second titanium nitride layeris preceded by the step of annealing the first titanium nitride layer byexposing the first titanium nitride layer to a gas comprising NH₃ at atemperature in a range between 530° C. and 680° C.
 13. The method ofclaim 12, further comprising the steps of annealing the second titaniumnitride layer by exposing the second titanium nitride layer to a gascomprising NH₃ at a temperature in a range between 530° C. and 680° C.14. The method of claim 7, wherein said step of depositing a secondtitanium nitride layer is preceded by the step of annealing the firsttitanium nitride layer by exposing the first titanium nitride layer to agas comprising NH₃ at a temperature in a range between 530° C. and 680°C. and at a pressure of less than about 3 Torr.
 15. The method of claim14, wherein said step of depositing a first titanium nitride layer ispreceded by the step of exposing the substrate to a gas consistingessentially of NH₃ at a temperature in a range between 530° C. and 680°C. and at a pressure of about 0.3 Torr.
 16. A method of forming atitanium nitride composite layer, comprising the steps of: depositing afirst titanium nitride layer on a substrate by exposing the substrate toa first composite gas consisting essentially of TiCl₄ and NH₃ atrespective first levels that establish a first ratio of TiCl₄ to NH₃ ina range between about 0.02 and 0.05 so that a ratio of chlorine atoms tonitrogen atoms in the first composite gas is in a range between about0.08 and 0.2; depositing a second titanium nitride layer on the firsttitanium nitride layer by exposing the first titanium nitride layer to asecond composite gas containing TiCl₄ and NH₃ at respective secondlevels that establish a second ratio of TiCl₄ to NH₃ that is greaterthan the first ratio: annealing the second titanium nitride layer byexposing the second titanium nitride layer to a gas consistingessentially of NH₃; and then depositing a third titanium nitride layeron the second titanium nitride layer by exposing the second titaniumnitride layer to a third composite gas containing TiCl₄ and NH₃ atrespective third levels that establish a third ratio of TiCl₄ to NH₃that is less than the second ratio: wherein the first ratio equals thethird ratio.